Well, its not official yet, but Microsoft's Windows 7 has now become the most widely used operating system. . . Windows 7 now has a strong 40.21% share of all desktop operating systems around the world whereas, the usage share of Windows XP has slipped to 38.64%. All this happened a couple of days back (in October). The rise in usage of Windows 7 and the drop in usage of Windows XP has been consistent since the time Windows 7 was first launched.